For security and ease of use' sake it really is useful to provide a standardized interface for deploying applications through Apple's own update channels. I don't see why Apple can't manage feature parity with most of the major Linux distributions. Something like universe in Ubuntu would greatly benefit OS X users.

That is very different from asking Apple to promote apps - just host them, police malicious apps, and take a small cut of profits for the service. Admittedly, that's a bit different from a package manager, but it's clear, consistent, and really the best option for Mac UX.